Kelly and Tweeters,

Even if the occasional Common Nighthawk is captured by a
Peregrine, I am quite certain this is not a significant factor in the
decline of nighthawks.

The decline of Common Nighthawks, from a status of common in the late
1960s and early 1970s to rare today, has occurred over a huge area.
The decline covers, at a minimum, south coastal BC and all of
Washington and Oregon west of the Cascades. Most of this area
has NO nesting Peregrines. (E.g., in Greater Vancouver, with well over
2 million people and formerly hundreds of pairs of nighthawks,
there were and are no breeding Peregrines.)

Declines in flying insects are often suggested as a reason for the decline
of Nighthawks. However, I know of no evidence for any such declines.
As Stan Kostka has pointed out, other species (e.g. swallows) that
depend on flying insects have shown no sign of declines-- if anything,
just the opposite. Yes, "biological insecticides" such as Bt
(Bacillus thuringiensis) have been used in efforts to control gypsy moths
and possibly other insect pests. However, these control efforts have
occurred in very local areas. The strains of Bt used normally affect
Lepidoptera only-- not all insects. And, for a number of reasons, any
local declines even in Lepidoptera are unlikely to persist for than 2-3
years
if a Bt application is not repeated in later years. (I have done extensive
research on this subject.)

The fact is, we simply don't know why Common Nighthawk populations
have declined so dramatically over such a huge area. However, it is very
unlikely to have anything to do with either Peregrines or Bt.

The theory that increased predation by crows is the main factor in the
nighthawk decline makes more sense to me than any other theory.
At least in my area-- Greater Vancouver-- crow populations have increased
by a factor of at least 4 since 1970. Crows are effective and tireless
predators of bird eggs and newly-hatched young. I'm sure that a number
of species have suffered from the proliferation of crows, but
nighthawks seem to have suffered the worst.

Hypotheses make a poor substitute for documented facts. However, it's
difficult to study the reasons for the decline of a species which is almost
gone (west of the Cascades). We should have been studying Nighthawk
breeding biology 20 years ago, when they were declining but not yet
gone in our cities.

Fortunately, as noted both by Tweeters subscribers and by me in my travels
around western WA, Nighthawks actually seem to be increasing a little
in the last few years. I see them most often in and near clearcuts in
rural areas, but often not far from the big cities (e.g. in Kitsap Co.)
Maybe the crows haven't found those areas yet, or the nests are too well
concealed. Even though clearcuts will not be the salvation of Spotted Owls,
Marbled Murrelets, or many other species, perhaps they may help to
prevent Common Nighthawks from completely disappearing from
our area. So let's just be glad that clearcuts have some wildlife value,
rather than none at all, as some of us would like to believe.

Wayne C. Weber
Delta, BC
contopus at telus.net






----- Original Message -----
From: "Kelly McAllister" <mcallisters4 at comcast.net>
To: <tweeters at u.washington.edu>
Sent: Monday, July 03, 2006 8:44 PM
Subject: Re: [Tweeters] RE: Nighthawks - ? The Kevin Li Memorial
NighthawkRoofTrail?


Interesting, as always, Stewart.

I wonder if peregrines take many nighthawks. There are some birds that
peregrines really get the best of, on a regular basis. Homing pigeons and
Rock Pigeons both come to mind. Bufflehead seem to be taken frequently.
Nighthawks are definitely agile in the air, perhaps too agile to be regular
peregrine prey. On the other hand, their habit of flying about in wide open
spaces might make them vulnerable.

I was just trying to think of alternative "limiting factors" besides nesting
habitat and crows. Certainly, changes in abundance of flying insects might
be another. Can you say Bt?

Kelly McAllister